Optogalvanic signals from argon metastables in a rf glow discharge

Laser optogalvanic (LOG) signals at 667.7, 751.5, and 696.5 nm from the 3 P1 and 3 P2 levels of Ar were studied at a pressure of 250 mTorr in a rf glow discharge. Signals with unexpected signs and time dependences were found. The results are interpreted as being due to radiative trapping effects and collisional mixing between resonance and metastable levels. An average electron energy of 2.1 eV is derived from modeling the data.